Rockwell hardness testing apparatus



May l1, 1955 1 .TsCHlRF ETAL 3,182,491y

ROCKWELL HARDNESS TESTING APPARATUS Filed D e. 1.4. 1959 2 Sheets-Sheet 1 .fla 1 fi a Al 52 6 "8 g1 10 [Nn/sw roes j wow/cf TscHzRF FRITZ GARTNER /Qyn May l1, 1965 Filed Dec. 14, 1959 l.. TscHlRF ETAL 3,182,491

ROCKWELL HARDNESS TESTING APPARATUS 2 Sheets-Sheet 2 FIG. 2

/NvE/vrags LUDk//Cf TSCHIRF FRITZ- G14/ T/VER United States Patent s claims. (ci. Pls-ss) This invention nelates to a Rockwell hardness testing apparatus.

In most olf the known Rockwell hardness testing apparatus the initial load acts on the plunger of the indenter before the actual tes-ting openation. In this case the point of the indenter often projects over the contact surface of the testing head thus causing contact with the reference plane which is defined by the surface of the test specimen during the test so that the indenter must be lifted from the specimento the reference plane during the gripping of the test specimen. Particularly in portable hardness testing apparatus this mode of operation may involve damage to the indenter during the gripping operation and errors may enter into the measurement if the contact surface of the apparatus slides on the test specimen during gripping.

In the Rockwell hardness testing apparatus according to the invention these disadvantages are avoided in that it comprises a retracting device which retracts the indenter behind the gripping surface.

In one embodiment of the invention the retracting device comprises a spring, which is disposed between the testing head and a bushing slidably guided in the base member and mounting the plunger firmly connected to the indenter, by which spring the bushing is held against an eccentric which is rotatably mounted in the base member and they bushing, is provided wim engaging faces which during the upward movement of the eccentric engage stops provided on the base mem-ber.

A particularly simple testing 'apparatus is obtained if, accordingvto la further feature of the invention, a single eccentric is provided for operating the reti-acting device and ffor applying the added load.

According to the inventionv the central part of the eccentric is preferably ilattened on one side and the fiat when in la position. normal to the longitudinal axis of the apparatus determines the initial load position.

In a development of the invention the apparatus is provided, preferably at vritsrbase member, with stops for a pin or the like carried by the eccentric, which stops determine the retracted position and the main load position.

A further featurewof the invention consists therein that a feeler pin extending between the .plunger and the dial gauge substantially along the axis of the apparatus is at its top end mounted in a pendulum bearing, the latter for example being a ball. This obviates damaging of the indenter tip if during the testing operation, a minimal lateral displacement of the piece to be tested with respect to the gripping surface should take place, should the testing piece .be subjected to .a heavy transverse force. Furthermore all friction iniiuences on the accuracy of the measurement are obviated since no other bearing of the plunger and feeler pin than at the top end of the latter is provided.

Further details and advantages lof the invention will be explained hereinafter with reference to the accompanying drawings, FIG. 1 is a longitudinal sectional View show ing an embodiment of 1a portable Rockwell hardness testing apparatus according to the invention, carrying a dial gauge, in the initial load position. FIG. 2 is an enlarged sectional View taken on. line II-II of FIG. l and showing the arnangement of the eccentric. FIG. 3 is ice an elevation showing an arrangement of stops by which the retracted position and the main load position are determined. FIG. 4 is .a side View illustrating a key for the operation olf the testing apparatus laccording to the invention.

A housing consisting of an outer sleeve 12 and a base member 11 firmly screwed thereto by a screw thread 13 accommodates the added load spring 2@ and the initial load spring 24, which produces the initial load of, e.g., 10 kilognams required in the Rockwell hardness testing method. The added load spring 2t) is contained in a spring bushing 14, which is screwed into the outer sleeve 12 by means of a screw cover 15 having an external screw thread 16.

The screw cover 15 has a conical opening 37, through which a slotted clamping cone 38 is pulled by a cap nut 39 to clamp the shaft 40 of the dial gauge 41. A pot-shaped part 42 welded to the underside of the screw cover 15 has a at bottom surface 43, which is formed with an opening 53 and forms a lower stop 54 for the shaft 40 of the dial gauge.

The feeler pin 27 of the apparatus carries at its top end a ball 44, which is centrally guided in a bore 45 of the screw 34, and establishes a connection to the feeler pin 46 of lthe dial gauge 41.

The added load spring 2t) is stressed by a screw 21 which has holes 23 and is screwed into a screw thread 22 provided on the inside of the spring bushing 14. The holes 23 serve for tightening the screw 21 in order to adjust the added load spring 20. An appropriate key (FIG. 4) can be inserted into the holes 23.

The initial load spring 24 is strained by the screw 34, which is screwed into the screw thread 22 of the spring bushing 14. Locking screws 35 provided in the screw 34 have conically tapered ends bearing on the surface of the screw 21 also screwed into the screw thread 22 of the spring bushing 14 to lock the two screws 21, 34 in the spring bushing 14. Screwdriver slots 36 serve for tightening the screws 35.

The basemember 11 has a depending cylindrical extension 50, which has `a screw thread 49 on which the conical testing head 48 is screwed, the gripping surf-ace 2 of which coincides with the test surface o-f the test specimen 47 if the apparatus is correctly fixed. The base member 11 has slidably guided therein a bushing 4, in which the plunger 6 is mounted, which is firmly connected to the indenter 1, e.g., with a screw 10. In a cavity S1 formed in the interior of the testing head 48 a spring 3y is arranged between the bushing 4 tand the testing head 48 and urges the bushing 4 against an eccentric 5 which is rotatably mounted in the base member 11 and is provided at one end with an eccentric lever 8 having a bal-l handle 9. Spring 3 exerts a force greater than the force of initial load spring Z4. 'Ihe eccentric S has preferably .a unilateral-ly flattened central portion 5 and extends clear through -a bore 3d which is at right angles to the longitudinal axis of the plunger 6.

The initial load spring 24 acts through the intermediary of a spring plate 25 on a collar 26 of the feeler pin 27, which is rigidly connected by a screw thread 28 to the plunger 6. Above the scr-ew `thread 2S the feeler pin 27 is enlarged to 'form `a shoulder 29, which engages the plunger 6. The initial load spring 24 is located in a tube 31 the lower part of which lis forced on .a cylindrical extension 32 of the spring plate 7 .controlled by the eccentric 5. The upper part `of the tube 31 is guided in a-bore 33 of the screw 21.

Some spacing balls 17 serve for centering the spring plate 7 relative to the base member 11. These balls are embraced by the spring bushing 14 .at Aa bore 18 thereof. The spr-ing bushing 14 bears on the base member 11 by means of an inwardly directed ilange 19. The spring bushing 14 has also two diametrically opposite aperturesk f indenter is in retracted position, the spring `3i being` re-y laxed and the springs 24 and 20 being stressed, and is clamped on the specimen with a -force which exceeds the.

test load. Theeccentric is then lloweredwby means of the eccentric lever 8 to move the apparatus into the ini-` tial load position shown in FIG.:1, in which the springN 3 is strainedand the initi-al.load spring24 =is relaxed whereby the initial load oil() kilograms is applied to the. Y test specimen 47. To retain the ececntric 5 in this position it is preferably provided Awith' a at 5'7', which in this v position lies snugly `against the spring plate 7 (FIG. 2). A rfurther rotation of the eccentric 5v 'causes vthe added load spring y20 to rel-ax whereby the main load, 'which consists of the -initial'and added loads, is .gradually applied. Aiiter the added load has been removed by -returning the eccentric 5 to the initial load position the hardness value vis read while the initial load is reapplied. The `ret-urn movement of the eccentric 5 is then continued to move the apparatus to the retractedr position, in which the .point of the indenter 1 is retracted behind the gripping surface V2 of -the testing head 48and is thus protected from -being damaged. This'retraction is effected by con tacting of the ,centrifyirig facev 4 of the 'bushing `4 with the counter lfaces or stops 6' ofthe plunger 6, -the latter being thereby lifted together withthe indenter l1 centrically behind the gripping surface 2. Y

To simplify the `operation ofthe apparatus it is recommendab-le to provide stops 56-for a pin 57 or the like i carried by the eccentric 5 in order` to limit .the rotationl of the eccentric. These stops are preferably provided on the base membery `11. .The pin 57 engages one ont these ,stops 56 -in theretracted position and another in.

the main load position (FIG. 3).

Y FIG. 2 shows distinctly ythe geometrical relations which must be observedto ensure .a satisfactory function of the apparatus: The eccentricity s, i.e.l1alf of the stroke of the eccentric, mustfbe larger than the vertical clearance a between the spring plate -7 and the plunger 6 and must Ialso be largerthan the vertical clearance b between the stops 6 of the plunger 6 and the engaging faces 4 of the 45 bushing 4.

TheV hardness testing apparatus according to the invention may be used n a .known manner as a stationaryA apparatus or, when inserted in special strainingk devices rfor various testing purposes, as a portable apparatus.v

What we claimis:

1. Rockwell hardness testing apparatus comprising an indenter, elementsnfor producing an initial load and a. 1

-niain load, ra mechanismincluding a plunger for applying said'loadsk to and kremoving said loads Ifrom the in-r 5 denter, said :indenter being firmly connected to said plunger, means tor measuring `the indenting depth opertracting device comprising a testing head surrounding-said indenter and having a specimen engaging lgripping suraoe, -abase member rigidly connected `to said testing head, a bushing slidably guided inV said lbase member, a spring connected between said head and said bushing, an eccentric rotatably mounted insaid base member against which said bushing is heldfby said spring, vsaid lever being operatively connected to rotate said eccentric, said bushing engaging a portion of -said plunger upon rotation of said eccentric,- said plunger together with said indenter thereby being lifted behind the gripping surface.

2. vA Rockwell hardness testingapparatus as claimed in claim 1, wherein they apparatus isfprovided `with rotation limiting stopsfor saideccentric, which stopsdeterrnine the-indenter retracted position and the main load position of said eccentric. Y

3. ARockwell hardness testing apparatus .as claimed in claim 2,l wherein said stops are carried by the baseV member.r

4. A Rockwell hardness testing apparatus` as claimed in claimk 1, whereinthe centralipart of lsaid eccentric is 5. vRock-well hardness testing apparatus `as claimedrin t claim l including cooperating conical surfaces on said bushing and said plunger whereby s-aid plunger is held centrally to said bushing when said indenter is retracted. 6.l Rockwell hardness testing` apparatus a'sclaimed in claim 1, wherein a pinris carried by-saidieccentric, and stops are provided -for said pin onsaid base member.

n 7. Rockwell hardness.testingapparatus as claimed'in claim l, wherein the elements for producing ythe initial and the main loads` comprise a sleeve and .springs jointly mounted wvithin said sleeve.

"8. Rockwell .hardness testing vapparatus as claimed in claim 1, whereinsaid means for measuring the indenting depth comprises a dial gauge anda feeler pin extending lbetweensaid plunger and said dialegauge.

References Citedby the Examiner UNITED STATES PATENTS :RICHARD C; QUEISSER, Primary Eixamineri C. A. CUTTING, `ROBERT Li' EVANS; JOSEPH P.

STRIZAK, Examiners. 

1. ROCKWELL HARDNESS TESTING APPARATUS COMPRISING AN INDENTER, ELEMENTS FOR PRODUCING AN INITIAL LOAD AND A MAIN LOAD, A MECHANISM INCLUDING A PLUNGER FOR APPLYING SAID LOADS TO AND REMOVING SAID LOADS FROM THE INDENTER, SAID INDENTER BEING FIRMLY CONNECTED TO SAID PLUNGER, MEANS FOR MEASURING THE INDENTING DEPTH OPERABLY CONNECTED TO SAID PLUNGER, A RETRACTING DEVICE FOR THE INDENTER, CHARACTERIZED IN THAT FOR THE SUCCESSIVE APPLICATION OF THE INITIAL LOAD, OF THE MAIN LOAD AND FOR RETRACTING THE INDENTER A SINGLE LEVER IS PROVIDED, SAID RETRACTING DEVICE COMPRISING A TESTING HEAD SURROUNDING SAID INDENTER AND HAVING A SPECIMEN ENGAGING GRIPPING SURFACE, A BASE MEMBER RIGIDLY CONNECTED TO SAID TESTING HEAD, A BUSHING SLIDABLY GUIDED IN SAID BASE MEMBER, A SPRING CONNECTED BETWEEN SAID HEAD AND SAID BUSHING, AN ECCENTRIC ROTATABLY MOUNTED IN SAID BASE MEMBER AGAINST WHICH SAID BUSHING IS HELD BY SAID SPRING, SAID LEVER BEING OPERATIVELY CONNECTED TO ROTATE SAID ECCENTRIC, SAID BUSHING ENGAGING A PORTION OF SAID PLUNGER UPON ROTATION OF SAID ECCENTRIC, SAID PLUNGER TOGETHER WITH SAID INDENTER THEREBY BEING LIFTED BEHIND THE GRIPPING SURFACE. 